1. Field of the Invention
The present invention relates to a film formation apparatus that is used for film formation of a material that can be performed on a substrate and a manufacturing apparatus having the film formation apparatus. Further, the present invention relates to a film formation method with the use of the film formation apparatus. Further, the present invention relates to a light-emitting device including, as a light-emitting layer, a layer containing an organic compound that is formed with the film formation apparatus, and a method for manufacturing the light-emitting device.
2. Description of the Related Art
A light-emitting element containing an organic compound as a luminous body, which has features of thinness, lightness, high-speed response, and low voltage driving, is expected to be applied to a next-generation flat panel display. In particular, a display device in which light-emitting elements are arranged in matrix is considered to have advantages in a wide viewing angle and excellent visibility over a conventional liquid crystal display device.
A light-emitting mechanism of a light-emitting element is as follows: by application of a voltage between a pair of electrodes where a layer containing an organic compound is interposed, electrons injected from a cathode and holes injected from an anode are recombined with each other at an emitting center of the organic compound layer to form molecular excitons, and the molecular excitons release energy in returning to the ground state to emit light. Singlet excitation and triplet excitation are known as excited states, and it has been considered that light emission can be achieved through either of the excited states.
Further, a layer containing an organic compound has a stacked-layer structure typified by a stacked structure of a hole transport layer, a light-emitting layer, and an electron transport layer. Further, EL materials for forming EL layers are roughly classified into low molecular (monomer) materials and high molecular (polymer) materials, and film formation of a low molecular material is performed with a vapor-deposition apparatus.
A conventional vapor-deposition apparatus includes a substrate holder at which a substrate is set, a crucible (or a vapor-deposition boat) in which an EL material, that is, a vapor-deposition material is sealed, a shutter to prevent the rising of a sublimating EL material, and a heater to heat the EL material in the crucible. Then, the EL material heated by the heater sublimates to form a film over a rotating substrate. In the conventional vapor-deposition apparatus, for forming a uniform film, an enough distance between vapor-deposition source and substrate and substrate rotation are needed.
For example, in the case of using a substrate having a size of 300 mm×360 mm, a distance of more than or equal to 1 m is needed between the vapor-deposition source and the substrate. The larger the size of the substrate is, the longer the distance between the substrate and the crucible is needed proportionately. Therefore, there is a problem in that the whole size of the vapor-deposition apparatus is large and the structure of the apparatus is complicated.
Further, since the distance between the vapor-deposition source and the substrate is large, a material is scattered on the portion other than an object on which film formation is performed so that the amount of material attachment to an inner wall of a film formation chamber or the like is increased, which leads to degradation of material use efficiency and increase in frequency of maintenance of the device.
Further, since the distance between the vapor-deposition source and the substrate is large, the film formation speed is low and exhaust air in the film formation chamber takes a long time so that the throughput is reduced.
Further, a technique in which an organic EL transfer substrate obtained by forming a film of a light-emitting organic compound on at least one surface of a heat-resistant film is heated by heat bars so that the light-emitting organic compound is transferred to a transparent substrate having a transparent electrode is disclosed in Patent Document 1 (: Japanese Published Patent Application No. 2000-77182).
Further, a technique in which a donor sheet including a chromogenic organic donor layer and a substrate that are in contact with each other are irradiated with a radiant ray so that an organic material layer is formed on the substrate is disclosed in Patent Document 2 (: Japanese Published Patent Application No. 2003-308974).
Further, a technique in which a donor sheet provided with an organic donor material is heated by a roll-to-roll method so that a layer of an organic material is formed over a substrate is disclosed in Patent Document 3 (: Japanese Published Patent Application No. Hei10-245547).